Walt Kowalski, portrayed by Clint Eastwood, is a gruff and cantankerous retired factory worker and war veteran, who recently lost his beloved wife Dorothy after a 50-year marriage. Struggling with grief, he lives alone in his once-thriving Highland Park neighborhood in Detroit, now overrun by poor Asian immigrants and rampant gang violence. Despite the deteriorating surroundings, Walt's home remains meticulously maintained, a stark contrast to the rest of the area.
His emotional detachment extends to his family, which includes two sons, Mitch and Steve. Both men, burdened with the belief that they can never impress their father, lead relatively normal lives while feeling the weight of Walt's disappointment. Tensions flare when Walt criticizes his grandchildren, Ashley and Josh, for their disrespectful behavior at Dorothy's funeral. When Mitch suggests that Walt moves to a retirement community, he outright refuses, sensing their ulterior motives for his possessions, including his prized Gran Torino and treasured jewelry.
Adding to Walt's struggles is his declining health; he suffers from severe coughing fits while refusing to admit his condition to anyone, even as his cough worsens and blood appears. Though a young priest, Father Janovic attempts to offer comfort, Walt calls him a “27-year-old over-educated virgin” and dismisses the notion of confessing, proclaiming he only attended church to please Dorothy.
Things take a turn when Walt encounters his new Hmong neighbors, particularly when he catches Thao Vang Lor, played by Bee Vang, trying to steal his Gran Torino as part of a gang initiation. Ready to take matters into his own hands, Walt brandishes his rifle but ultimately decides to spare Thao. This act of unexpected leniency earns him respect from the Hmong community when he later defends Thao from gang members with his rifle, prompting the neighbors to thank him with gifts.
Backed by his family, Thao's mother insists he work for Walt to repay his wrongdoing, allowing the two to forge a relationship built on respect. Sue, Thao's sister, introduces Walt to her culture, shedding light on the Hmong's traditions and values. Grudgingly, Walt begins to mentor Thao, setting him up with a job while earning Sue's gratitude when he protects her from menacing gangsters. At a family gathering, Walt learns about the Hmong belief regarding the soul and realizes the warmth missing in his own family relationships.
However, Walt's health continues to decline, and he's soon confronted with a grim diagnosis. Tensions escalate when gang members retaliate against Thao, launching an attack on the Vang Lor household, resulting in severe injuries and a horrifying ordeal for Sue. With no law enforcement assistance, they turn to Walt for help.
Taking steps towards personal closure, Walt prepares for what he knows must be a final confrontation. He buys a suit, gets a fresh haircut, and confesses to Father Janovic. When Thao returns, Walt imparts his Silver Star, urging Thao not to bear the burden of killing someone as he has.
During his ultimate stand-off with the gang, Walt deliberately puts himself in harm's way, drawing their fire as he wields nothing but an army lighter, a move designed to end his suffering and reclaim his lost honor. After a tense exchange, his sacrifice leads to Thao and Sue's safety. Walt's funeral, celebrated by Father Janovic, sees an unexpected turnout from both his family and the Hmong community, signaling the profound impact he had on those around him. In a final twist upon reading his will, Walt leaves his estate to the church while gifting Thao his cherished Gran Torino, instructing him to keep it unchanged. The film closes with Thao driving along Lakeshore Drive, accompanied by Walt's dog, Daisy, embodying the meaningful legacy left behind.
